The engine disk that fell apart and caused a fire aboard an American Airlines jet revealed a problem with a common alloy that hadn't been detected in 30 years, the manufacturer GE Aviation told airlines on Friday.

Only one plane is still in operation with a disk from the same batch of alloy, called Inconel 718, and GE said in its letter to airlines that it is working with the unidentified airline to remove that part from service. Investigators must determine whether the microscopic manufacturing flaw could affect other engines.

"GE Aviation has not experienced a failure from an engine component caused by an anomaly in Inconel 718 material in more than 30 years," said Rick Kennedy, a company spokesman. "What the investigation will do now is move forward to determine if there is a suspect population of engines that need to be addressed, to make sure the fleet is fully protected."

The National Transportation Safety Board continues to investigate the incident Oct. 28 involving American flight 383 at Chicago’s O’Hare airport. The pilots aborted a takeoff and all 161 passengers and nine crew members evacuated from the plane before a fuel leak from the broken engine caused a fire.

Investigators revealed Friday that a turbine disk failed in the right engine of the Boeing 767-300, hurling at least four parts up to a half-mile away. The disk showed signs of fatigue despite having gone through only about 11,000 flights of its life-limit of 15,000, investigators said.

The disk’s metallurgy is being evaluated because the microscopic problem during manufacturing might not have been evident in inspections during the 19 years the plane was flying. The anomaly has been identified and is being further evaluated, according to the GE Aviation letter.

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An American Airlines flight bound for Miami caught fire on a runway at O'Hare International Airport Friday afternoon as it was taking off, officials said. American Airlines said the plane aborted takeoff due to an "engine-related mechanical issue."
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The engine was a CF6-80C2. GE said the CF6 engines have been a workhorse of the industry since the 1970s, powering seven types of wide-body jets. More than 4,000 of the engines in the family are in service and they have accumulated more than 400 million flight hours.

The NTSB’s investigation could take months longer to determine what caused the problem and for recommendations to avoid a recurrence.

“As the investigation progresses, if there is a determination that additional action is required, GE will provide periodic updates to operators,” GE said in the letter.